In order to attain the effective use of limited resources, there have been proposed technologies for taking out electric energy through conversion of various types of energy. One of them is technology for taking out electric energy through conversion of vibration energy. For example, Patent Document 1 given below discloses a piezoelectric-type power generating element in which a layered piezoelectric element is laminated to form a piezoelectric element for power generation, and an external force is used to cause the piezoelectric element for power generation to vibrate, thereby generating electric power. Further, Patent Document 2 discloses a power generating element which has a MEMS (Micro Electro Mechanical System) structure using a silicon substrate.
On the other hand, Patent Document 3 discloses a type of power generating element in which a hammer-head like structure body for supporting a weight body by a cantilever beam, one end of which is fixed, is used to cause the weight body which constitutes a head portion to vibrate, thereby generating electric power by the use of a piezoelectric element for power generation arranged at a handle portion. Further, Patent Document 4 discloses a piezoelectric element which uses a structure body for supporting a weight body by a plate-like bridge portion which is bent in the L letter shape, together with a power generating element which uses the hammer-head like structure body.
A basic principle of these power generating elements is to impart periodic deflection to a piezoelectric element by vibration of a weight body, thereby taking out to the outside charge generated on the basis of stress applied to the piezoelectric element. The power generating elements are mounted on, for example, automobiles, trains and ships, by which vibration energy which is applied during transportation can be taken out as electric energy. Further, they are attached to vibration sources such as refrigerators and air conditioners, thus making it possible to generate electric power.